As electronic technology develops, high-definition digital televisions, high-end smartphones, or other portable broadcast devices are spreading, and accordingly, the demand for various reception schemes for broadcast services and support of a diversity of services is increasing. In particular, there is increasing demand for supporting various services, such as high-quality contents, interactive services, and multi-screen services for ultra-high definition television (UHDT).
Meeting such demand requires parallel development of devices for playing contents and configuring and representing techniques for generating contents and transmission technology for transferring contents. Among them, transmission techniques may be classified into physical aspect and logical aspect.
A broadcast service consists of one or more video and audio streams and may include multiple data streams as necessary. The logical aspect of transmission technology includes techniques for configuring a multiplex including one or more broadcast services and meta data necessary for playing the broadcast services and transmitting the same through one logical channel. Representative examples of such meta data include service configuration information, such as the type of broadcast service included in the multiplex, the type of video, audio, and data streams constituting an individual broadcast service, and information necessary to extract from the multiplex the broadcast service and individual streams constituting the broadcast service, and EPG-related information such as broadcast start/end time or synopsis. According to the conventional art, the meta data is generally transmitted through the signaling information of the data link layer (i.e., layer 2 (L2)).
Generally, two procedures are required to play a broadcast service. That is, the receiving part playing broadcast service receives L2 signaling information transmitted through the L2 layer to obtain service configuration information necessary for playing individual broadcast services, and in case the user selects some broadcast service, receives the video, audio, and data streams from the transmission medium using the individual stream information constituting the broadcast service from the obtained service configuration information.
The L2 signaling information may be converted into a corresponding frequency and extracted in real-time whenever the user selects any broadcast service, or the L2 signaling information transmitted at each frequency through such an operation as channel scanning may be first obtained, cashed to the playing device, and used. The former case has a shortcoming in that the real-time processing increases the channel zapping time while the latter one may not play the broadcast service if the cached information is not consistent with the signaling information actually transmitted. Accordingly, in order to address the above problems, in case the signaling information is cached by the receiving part and used, comparison in version information is made between the stored information and the signaling information actually transmitted to identify whether they are consistent with each other, and if they are of the same version, the stored information may be then used as its to play the broadcast service. If they are inconsistent with each other, latest L2 signaling information may be obtained to update the existing stored information and the broadcast service is then played. However, the approach through simple comparison in version information has potential problems in light of shortening the channel zapping time. For example, L2 signaling information may break down into information directly associated with actually playing broadcast service and information not directly associated therewith. Accordingly, in case the information not directly associated with the play of broadcast service of the stored L2 signaling information is varied, since the broadcast service may be played using the stored existing information, no problem arises with playing the broadcast service even without updating the L2 signaling information in real-time.
As an example of the transmission technique in the physical aspect, such broadcast communication standard as digital video broadcasting the second generation terrestrial (DVB-T2) has been developed. DVB-T2 is a second generation European terrestrial digital broadcast standard as an evolution of DVB-T, which has been adopted thus far as standard by 35 countries or more worldwide including the European countries and is now in service. DVB-T2 employs the state-of-art techniques, such as low density parity check (LDPC) code and 256 quadrature amplitude modulation (256QAM) schemes to increase transmission capacity and implement higher bandwidth efficiency. Further, this standard has adopted a logical channel called physical layer pipe (PLP) for physical signal frames and may thus provide various high-quality services, e.g., HDTV, through the limited bandwidth.
Further, DVB-T2 includes a physical layer (i.e., layer 1 (L1) signaling area in each frame to process data and may more efficiently process data depending on the information contained in the L1 signaling area.